Nervous System Overview and Action Potentials

Question 1

what is the difference between NS and ES?

Answer 1

NS is a quick fix to homeostatic disturbance and ES is a slower and long term maintenance.

Question 2

what is neuroglia?

Answer 2

support cells for neurons

Question 3

what are nissl bodies?

Answer 3

they are clusters of ribosomes found inside the cell body. So many present that the axon appears grey..

Lots of nissl bodies in grey matter

Question 4

Whare are oliogdendrocytes?

Answer 4

what forms the myelin for axons in CNS

Question 5

What are Schwann cells?

Answer 5

what forms the myelin for axons in PNS

Question 6

what is the function of myelinated axons?

Answer 6

to speed up the rate of nerve impulse conduction aka SALTATORY CONDUCTION

Question 7

what makes up a anaxonic neuron?

Answer 7

hard to tell the difference between dendrite and axon but they’re all connected to the cell body

USED FOR INTERNEURONS

Question 8

what makes up a bipolar neuron?

Answer 8

one dendrite, one axon, and a central cell body

FOUND IN SENSORY NEURONS

Question 9

what makes up a pseudounipolar neuron?

Answer 9

dendrite is continuous with the axon. Cell body is off to one side.

FOUND IN SENSORY NEURONS

Question 10

What makes up a multipolar neuron?

Answer 10

Multiple dendrites attached to a cell body, a primary axon

FOUND IN MOTOR AND INTERNEURONS

Question 11

what are the functional classifications of neurons?

Answer 11

• sensory
• motor
• interneurons

Question 12

what division of NS are sensory, motor and interneuron a part of

Answer 12

• Sensory: afferent division of PNS
• Motor: efferent division of PNS
• interneurons: ONLY in CNS

Question 13

how do sensory neurons carry information

Answer 13

from reflex receptor to CNS

Question 14

how do motor neurons carry commands?

Answer 14

from CNS to EFFECTORS

Question 15

where are the cell bodies/dendrites located for sensory and motor neurons?

Answer 15

Sensory: dendrites/cell body in PNS

Motor: dendrites/cell body in CNS

Question 16

how do interneurons carry information?

Answer 16

from one neuron to another

Question 17

that direction does information flow in?

Answer 17

one direction

Question 18

what are the two types of electrical signals in neurons?

Answer 18

action potential and graded potential

Question 19

what are some examples of graded potentials

Answer 19

EPSPs and IPSPs

Question 20

what are the differences between graded and action potentials

Answer 20

GP: longer lasting, small changes in Vm, travel short distances

AP: very fast changes in Vm, always the same with non change in strength or size as they travel along membrane.

Question 21

What does depolarization mean?

Answer 21

becomes more positive, EPSPs

Question 22

What does repolarization mean?

Answer 22

Vm returns to resting value

Question 23

What does hyperpolarization mean?

Answer 23

Vm becomes more negative than resting, IPSP

Question 24

how does depolarization occur?

Answer 24

Na+ moving into the cell through open voltage-gated Na+ channels through positive feedback

Question 25

What happens at the peak of AP

Answer 25

VG Na+ channels close and slow voltage gated K+ channels open transition from graded potentials to AP AT AXON HILLOCK

Question 26

what happens when a threshold is met for AP

Answer 26

EPSP reaches threshold and causes voltage gated Na+ channels to open

Question 27

what happens during repolarization

Answer 27

K+ moves outside of the cell, through open VG K+ channels

Question 28

what happens during hyperpolarization

Answer 28

VG K+ channels are still open and then they begin to close

Question 29

What is the V-gate Na+ activation gate?

Answer 29

Closed at resting Vm and they quickly open at threshold depolarization

Question 30

What is the V-gate Na+ inactivation gate?

Answer 30

They open at resting Vm and slowly close at threshold depolarization

Question 31

will the V-gate Na+ inactivation and activation gate be open at the same time?

Answer 31

Yes since activation opens quickly and inactivation closes slowly they overlap

Question 32

in what conditions with the V-gate Na+ inactivation gate work under?

Answer 32

will ONLY function again if the channel is back at the resting membrane potential, will not be functioning unless at rest.

Question 33

V-gate K+ channel how does it work?

Answer 33

begins to open at the threshold, but it is SLOW. Delayed by the same time as the V-gated Na+ inactivation gate

Question 34

the activation of Na+ channels during an AP occur in a positive or negative feedback? How?

Answer 34

POSITIVE. Na+ channel activation gates open rapidly. Na+ enters the cell. Which causes more depolarization of the cell. This means more Na+ channels get activated.

Question 35

What stops a Na+ channel during an AP?

Answer 35

The slower Na+ channel inactivation gate closes

Question 36

How does the absolute refractory period work?

Answer 36

IMPOSSIBLE FOR CELL TO FIRE ANOTHER AP. This is due to an all or none activation and the V-gated Na+ channels closed inactivation gates.

Question 37

How does the relative refractory period work?

Answer 37

A larger than normal EPSP and elicit an AP. This is due to some Na+ channels resetting to resting state. After hyperpolarization

Question 38

what keeps the AP flowing in one direction

Answer 38

the absolute and relative refractory periods

Question 39

How does hyperkalemia influence neuron excitability

Answer 39

increase of K+ If inbetween 3.5 and 6: There is an increase of K+ that causes membrane excitability. Depolarizes Vm moving closer to threshold. If larger than 6. There is a reduction in neuron excitability. Depolarizes membrane and causes inactivation of V-gated Na+ channels

Question 40

How does hypokalemia influence neuron excitability

Answer 40

decrease of K+ reduces membrane excitability. Hyperpolarizes membrane further from threshold.

Question 41

How does hypercalcemia influence neuron excitability

Answer 41

If there is too many Ca2+ in ECF it will reduce membrane excitability.

Question 42

How does hypocalcemia influence neuron excitability

Answer 42

with not enough Ca2+ in the ECF it will increase membrane excitability

Question 43

Explain what the local current flow is during an AP

Answer 43

It is when a certain section of an axon is experiencing depolarization through V-gate Na+ channels opening and Na+ influxing in. Which will then cause depolarization of the next axon segment to reach threshold. The segment before beings to enter refractory period where K+ leaves the neuron.

Question 44

How does AP move along myelinated axons

Answer 44

AP jumps from node to node (saltatory conduction), this speeds up conduction velocity

Question 45

how can conduction of velocity of AP increase?

Answer 45

- if axons have myelin | - or if axons have bigger diameter

Question 46

what are two demyelination diseases?

Answer 46

Guillain-barre syndrome (CNS) Multiple Sclerosis (PNS)

Question 47

What is Multiple Sclerosis?

Answer 47

a demyelination disease. When myelin gets destroyed at the node of Ranvier. Since missing myelin a lot of Na+ will get out of the cell.